1. Field of the Invention
The present invention relates to a grinding method of a multifunction grinding machine grinding each of vicinities of both ends of a workpiece by each of two different grinding wheels of the multifunction grinding machine.
2. Description of the Related Art
Where a prior grinding machine grinds both end portions of a crankshaft for a combustion engine as shown in FIG. 6, it grinds a workpiece W held by a spindle equipment 120 providing a centering member 121 and a driving pin 123 and by an un-illustrated tail stock equipment providing a centering member 131.
In the prior grinding machine as shown in FIG. 6, the workpiece W is held by the centering members 121, 131 mounted oppositely on a spindle rotational axis ZW, and the driving pin is rotated around a workpiece rotational axis with being projected to the spindle rotational axis direction at an eccentric position from the spindle rotational axis ZW and engages with an adjacent crank portion Wk or a counter weight portion Ww to rotate the workpiece W around the spindle rotational axis. Therefore, the grinding wheel can not grind one end portion WTa of the workpiece at a side of driving pin but can grind the end portion WTb of the workpiece at a side of the centering member 131 of the tail stock equipment without the driving pin 123.
Since the profile of one end portion WTa of the workpiece and the profile of the other end portion WTb of the workpiece are different or a wheel slide interferes with a right or a left spindle head or with another portion of the workpiece, the prior grinding machine is prepared by two grinding machines. One grinding machine A is for grinding the one end portion WTa of the workpiece and the other grinding machine B is for grinding the other end portion WTb of the workpiece. The grinding machine A grinds the one end portion WTa of the workpiece after the workpiece W is set on the grinding machine A, then the ground workpiece is removed from the grinding machine A to be set on the grinding machine B where the other end portion WTb of the workpiece W is ground.
As another prior art, a multifunction grinding machine is provided to grind each of the one end portion WTa and the other end portion WTb of the workpiece by two kinds of the grinding wheels, a position change is required from the one end portion WTa to the other end portion WTb after grinding the one end portion WTa, then grind the other end portion WTb.
In other prior art disclosed in Japanese laid-open publication Tokkaihei 11-207576, a crankshaft is provided a female screw portion to be supported at one side by a centering member having a male screw portion engaging with the female screw portion and is supported at the other side by a centering member having no screw portion, and is rotated by a driving pin slide-able along a workpiece rotational axis direction at the other end of the workpiece. The one end portion of the crankshaft can be ground because the one end portion is supported by screw engagement mechanism. The other end portion of the crankshaft can be also ground by rotating by the screw engagement mechanism at the one side after the driving pin at the other side is moved to a position not to be engaged with the grinding wheel.
In further other prior art disclosed in Japanese Patent Tokkoushou 51-14186, it is provided first spindle head and second spindle head, each of which holds a workpiece by a chuck and supports the workpiece by a centering member, and the first and the second spindle heads are disposed oppositely. In relative to the first and the second spindle heads, each of the chucks is not moved but each of the centering members is shifted along the workpiece rotational axis with supporting the workpiece. By this construction, the further other prior art can grind the one end portion of the workpiece after holding the workpiece by the chuck at other side by shifting the centering member to the other side and can grind the other end portion of the workpiece after holding the workpiece by the chuck at one side by shifting the centering member to the one side.
The prior art disclosed in FIG. 6 needs two grinding machines grinding the one end portion and the other end portion respectively and separately. It needs much cost to prepare two grinding machines and needs floor space more to increase costs and decrease operation efficiency.
The prior multifunction grinding machine does not need two grinding machines but it needs to exchange the workpiece one to another to grind the other end portion after grinding the one end, thereby needs more operation and reduces its efficiency.
The other prior art disclosed in Japanese laid-open publication Tokkaihei 11-207576, the screw engagement mechanism drives the crankshaft when grinding the other end portion of the crankshaft, thereby to drive by small driving force so that it is possible not to drive by enough driving force.
The further other prior art disclosed in Japanese Patent Tokkoushou 51-14186, both of the first and the second spindle heads should have driving means to hold and release the chuck and rotational driving means to rotate the chuck, so that the construction is very complex.